When treating damaged or tumorous bodies of the vertebra, usually rigid longitudinal supports are used which are anchored by bone anchoring means, (e.g., pedicle screws or pedicle hooks). In this manner, a movement of the stabilized bodies of the vertebra relative to one another can be prevented, so that the fusion of the adjacent bodies of the vertebra is promoted.
One known device to fix vertebral bodies is made up of a number of tulip-shaped pedicle screws, but instead of the conventional rigid longitudinal support, the screws are connected with individual helical spring elements. Although the length of the helical springs can be adjusted, only a modification of the pretensioning force of the helical spring elements is achievable.
Another known device to fix vertebral bodies is also made up of a number of tulip-shaped pedicle screws, but instead of the conventional rigid longitudinal support, the screws are connected with individual damping elements. A disadvantage of these damping elements is their manufacture from a biocompatible material, resulting in the damping element having linear spring characteristics.
A further device to fix vertebral bodies with a number of pedicle screws and elastic connecting parts provided between each two pedicle screws parallel to the longitudinal axis of the spinal column is also known. This device comprises elastic connecting parts with progressive spring characteristics. The elastic means comprises a helical spring, the central bore of which is filled with a visco-elastic material. A disadvantage of this known device is that by constructing the elastic means with two elements having different spring characteristics, an elaborate manufacturing process of the elastic means is required.